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In 2002, a whale shark was tagged in Ningaloo Marine Park (off the north west coast of Australia) and tracked for over 2500km towards Christmas Island (south of Indonesia). Although always expected, this was the first proof that sharks from Ningaloo travel long distances away from the Australian coast. In order to expand this
programme, in January 2004, a team from the Australian marine conservation group ECOCEAN conducted a field trip to Christmas Island at the time
when whale sharks are usually sighted by the dive industry.
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Whale
sharks have been shown to migrate from Ningaloo
towards Christmas island.
Photo Udo Engelhardt |
In addition to one SPOT 2 satellite tag donated to the programme by MCSS, the team had four archival data-logging tags for deployment. Daily vessel surveys were undertaken between 9:00am - 4:00pm and 6:30pm - 10:00pm with assistance from the management agency Parks Australia North. The dive community was also on the look out for sharks and would radio to us if / when a shark was seen.
During the 7-day field trip, despite intensive effort, few whale sharks were sighted. This is not surprising given that the number of whale sharks sighted at Christmas Island has declined significantly over the last few years. This may be due to natural inter-annual variation, or it may be from increased fishing effort for this species in recent years.
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The Smart Position and Temperature Transmitting (SPOT2) Tag transmits whenever it is at the surface. The shark s location is determined by cross triangulation between the receiving Argos satellites. This type of tag is used to track the sharks movement as it travels across ocean basins.
Photo: David Rowat
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However, through the commitment of whale shark conservationists worldwide, the sharks are receiving greater protection through national legislation (e.g. Australia, India, Maldives, Philippines, Seychelles etc.) and through listing on international conventions (e.g. CITES, Convention on Migratory Species etc.).
The team was able to deploy the SPOT2 satellite tag on a 6.5m female whale shark. This shark stayed in the area for several days, with re-sightings occurring while the shark was feeding at the surface during surveys con-ducted on the following evening, and again two days later by a Japanese documentary-maker while he was on SCUBA at 26m depth. To date, no signals have been received by the satellite the shark may have simply remained deep, a satellite may not have been overhead while the shark was on the surface or the tag may have failed. Importantly, the technique for deployment was shown to be
successful, with this shark sighted several days after with the tag still attached. We still hope to hear from this shark and will keep you posted on any
results.
Unlike the SPOT2 tags, which communicated directly to the ARGOS
satellites, the archival tags need to be retrieved from the shark before the data can be downloaded, i.e. the shark needs to be re-sighted and the tag removed. We are confident of success, considering many of the sharks seen at Ningaloo each year are seen again in subsequent years. In addition to being tagged, the sharks were photographed and the identity of each recorded in the
ECOCEAN Whale Shark Photo-identification Library (Sagren vol
1.4).
A whale shark is identified (or marked ) through photo-identification with a record stored in the public online Library. When this shark and many others are
resighted we can recognize it as recaptured . This will help us document the movements of this highly migratory species, and also help us make an estimation on the number of whale sharks that are actually in the region (through mark/re-capture). The success of the project relies on public support. For this reason, we encourage everyone to please take down a few notes on where and when whale sharks have been sighted (with estimated length and sex if possible). In addition to the sighting data, identification photographs of the whale shark, especially the natural patterning behind the gill slits and any noticeable scars, can be submitted online to the Library
(www.ecocean.org). Your help in the conservation of whale sharks is much appreciated.
For more information about whale sharks in Australia visit:
ecocean.org
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